ENet is a pure Erlang network stack that can be used to encode and decode a variety of common packet formats.
The project includes a port program that can be used to send and receive ethernet frames via the /dev/tap0
device.
- Mac OS X
libevent
, OS X 10.6.1 (probably compatible with other versions), thetuntaposx
driver ( http://tuntaposx.sourceforge.net ) loaded,sudo
.- Linux
libevent, the
tun
module loaded, thetunctl
program (usually in theuml-utilities
package),
sudo``.
- Mac OS X
The
enet_tap
port program. Takes a mandatory option-f
to specify which tap device to use. (normally "/dev/tap0")- Linux
The
enet_tap
port program. Takes a mandatory-i
argument that specifies which tap device to use. (normally "tap0")
You'll need to edit the Makefile
to set the appropriate CFLAGS
and LDFLAGS
for your machine and erts
(32 or 64 bit build, location of libevent headers and libraries, ...).
For ease of use, you should probably change the ownership of /dev/tapN
to yourself.
You should create a tap device that you can open as your user. The easiest way to do this is to install the tunctl
program (in the uml-utilities
package on debian systems), and then create the device:
tunctl -u yourusername -t tap0
Enet currently uses the ifconfig
command to configure the operating system side of the tap device. This is usually a privileged operation, so we need to configure sudo to allow erlang to do this without a password.
Add the following lines to /etc/sudoers
:
Cmnd_Alias ENET = /sbin/ifconfig tap0 *
yourusername ALL=(ALL) NOPASSWD: ENET
From an erlang shell (erl -boot start_sasl -pa ebin
):
1> {ok, Pid} = enet_eth_iface:start("tap0", "192.168.2.1/24 up"),
{ok, Dumper} = enet_if_dump:attach(Pid).
You should now see decoded traffic in the erlang shell. If you ping the IP address of the erlang interface 192.168.2.2
in the example, you should see ping replies and an arp entry (arp -na
):
? (192.168.2.2) at 4a:6e:1:1b:19:8f on tap0 ifscope [ethernet]
There are a number of debugging aides available:
- * enet_if_crtest -- Tries to re-encode decoded packets and writes
erlang and pcap trace files if this fails.:
1> enet_host:start(test_h), enet_host:attach_iface(test_h, tap0, fun () -> enet_eth_iface:start("tap0", "192.168.2.1/24 up") end), enet_host:attach(test_h, tap0, fun (Pid) -> enet_if_dump:attach(Pid) end), enet_host:attach(test_h, tap0, fun (Pid) -> enet_arp_cache:attach(Pid) end).
# enet_if_arp:attach(Pid), # enet_if_arp:add_entry(Pid, "4A:6E:01:1B:19:8F", "192.168.2.2"), # enet_if_icmp:attach(Pid), # enet_if_crtest:attach(Pid, "priv/breakage").